Friday, September 2, 2011

Concrete Dock Pile Cap Longitudinal cracking and soffit delamination Repair

List -
Due to age and exposure a concrete dock pile cap exhibits numerous bents with pile caps that have a significant amount of longitudinal cracking on the sides of the pile cap and soffit delamination.  The tried and true repair for such an occurrence is to chip away the soffit of the pile cap and recast among other details I am leaving out. As you can imagine this is not an easy task because of low headroom, and rising tides.
An engineer in our office proposed that we 'hang' the pile cap from a new beam on top of the pile cap.  The pile cap is CIP and measures 1.5' deep by 2.5' wide. The precast concrete deck panels sit on top of the pile cap and a CIP closure strip measuring 2' deep by 1.5' wide is centered on the pile cap.  On top of the deck is 18" of ballast and asphalt.  The idea is to remove the 18" of ballast and asphalt and pour a CIP beam on top of the pile cap. The pile cap is shear controlled as the piles are spaced roughly 10' o.c.  The trick is how to hang the pile cap from the new beam. One idea is to drill holes into the existing pile cap (top down) that stop at half the depth of the pile cap and install headed anchors with epoxy.  I'd rather have ties installed but given the scenario this is not possible.  It is our opinion that this would be incredibly less expensive than building scaffolding under the pile cap, collecting demolition debris (and all other environmental constraints), dealing with working at low tides only (tidal fluctuations of roughly 8'-10' a day which limits the amount of time that work can be done), and then casting.
Does anyone have any other ideas?
I can provide a sketch upon request, please send an e-mail directly to me.
Andre Sidler, S.E., P.E.
Seattle, WA